Method of and apparatus for detecting an activated condition of a wide range air-fuel ratio sensor

Abstract

A method of detecting an activated condition of a wide range air-fuel ratio sensor is provided. With this method, application of a current to a heater is started idiately after an engine is started (S00). Then, a current Icp for pumping is passed through an electromotive force cell (S10). A lapse of a predetermined time Tin is waited for (S18). After a lapse of time Tin, a voltage Vs across both electrodes of the electromotive force cell is detected (S20) and labeled as Vs0 (S22). Then, application of Icp is suspended (S30) and a routine is held on standby until a time of 25 ms elapses (S35). At the point of time when the time of 25 ms has elapsed, the voltage across the electrodes on the opposite sides of the electromotive force cell is detected (S40) and labeled as Vs1 (S45). A resistance value Rs1 is calculated from Vs0, Vs1 and Icp (S50). The resistance value Rs1 is compared with a value Rss which has been prepared previously (S55) and it is judged, when Rs1 is smaller than Rss, that the electromotive force cell has been put into an activated condition. An apparatus for detecting an activated condition of a wide range air-fuel ratio sensor is also provided.

What is claimed is: 
     
       1. A method of detecting an activated condition of a wide range air-fuel ratio sensor, wherein the air-fuel ratio sensor includes two cells each having an oxygen ion conductive solid electrolytic body heated by a heater and two porous electrodes disposed on opposite sides of the oxygen ion conductive solid electrolytic body, respectively, the two cells being disposed so as to oppose each other with a gap therebetween, one of the cells serving as a pump cell pumping oxygen out of or into the gap, and the other of the cells serving as an electromotive force cell for generating a voltage according to a difference in oxygen concentration between an oxygen reference chamber and the gap, the method comprising the steps of: applying a current or voltage to the electromotive force cell;   detecting a voltage V0 across the electrodes at opposite side surfaces of the electromotive force cell;   suspending said step of applying a current or voltage after said voltage V0 becomes equal to or smaller than a predetermined value Vss ranging from 1.1 to 2.0 volts;   detecting a voltage V1 across the electrodes at the opposite side surfaces of the electromotive force cell after a lapse of time ranging from 10 ms to 50 ms after said suspending; and   detecting a resistance value Rs1 of the electromotive force cell on the basis of said voltage V0 and said voltage V1 and judging that the wide range air-fuel ratio sensor has been activated when said resistance value Rs1 is equal to or smaller than a predetermined value Rss ranging from 1 to 5 kΩ.   
     
     
       2. A method of detecting an activated condition of a wide range air-fuel ratio sensor, wherein the air-fuel ratio sensor includes two cells each having an oxygen ion conductive solid electrolytic body heated by a heater and two porous electrodes disposed on opposite sides of the oxygen ion conductive solid electrolytic body, respectively, the two cells being disposed so as to oppose each other with a gap therebetween, one of the cells serving as a pump cell for pumping oxygen out of or into the gap, and the other of the cells serving as an electromotive force cell for generating a voltage according to a difference in oxygen concentration between an oxygen reference chamber and the gap, the method comprising the steps of: applying a current or voltage to the electromotive force cell;   detecting a voltage V0 across the electrodes at opposite side surfaces of the electromotive force cell;   suspending said step of applying a current or voltage after the lapse of a predetermined time Ts ranging from 5 to 12 seconds after the heater starts being energized;   detecting a voltage V1 across the electrodes at the opposite side surfaces of the electromotive force cell after the lapse of time ranging from 10 ms to 50 ms after said suspending; and   detecting a resistance value Rs1 of the electromotive force cell on the basis of said voltage V0 and said voltage V1 and judging that the wide range air-fuel ratio sensor has been activated when said resistance value Rs1 is equal to or smaller than a predetermined value Rss ranging from 1 to 5 kΩ.   
     
     
       3. An apparatus for detecting an activated condition of a wide range air-fuel ratio sensor, the air-fuel ratio sensor including two cells each having an oxygen ion conductive solid electrolytic body heated by a heater and two porous electrodes disposed on opposite sides of the oxygen ion conductive solid electrolytic body, respectively, the two cells being disposed so as to oppose each other with a gap therebetween, one of the cells serving as a pump cell for pumping oxygen out of or into the gap, and the other of the cells serving as an electromotive force cell for generating a voltage according to a difference in oxygen concentration between an oxygen reference chamber and the gap, the apparatus comprising: current or voltage applying means for applying a current or voltage to the electromotive force cell;   V0 voltage detecting means for detecting a voltage V0 across the electrodes at opposite side surfaces of the electromotive force cell;   suspending means for suspending said applying of a current or voltage to the electromotive force cell after said voltage V0 becomes equal to or smaller than a predetermined value Vss ranging from 1.1 to 2.0 volts;   V1 voltage detecting means for detecting a voltage V1 across the electrodes at the opposite side surfaces of the electromotive force cell after a lapse of time ranging from 10 ms to 50 ms after said applying of a current or voltage to the electromotive force cell is suspended; and   activity detecting means for detecting a resistance value Rs1 of the electromotive force cell on the basis of said voltage V0 and said voltage V1 and judging that the wide range air-fuel ratio sensor has been activated when said resistance value Rs1 is equal to or smaller than a predetermined value Rss ranging from 1 to 5 kΩ.   
     
     
       4. An apparatus for detecting an activated condition of a wide range air-fuel ratio sensor, the air-fuel ratio sensor including two cells each having an oxygen ion conductive solid electrolytic body heated by a heater and two porous electrodes disposed on opposite sides of the oxygen ion conductive solid electrolytic body, respectively, the two cells being disposed so as to oppose each other with a gap therebetween, one of the cells serving as a pump cell for pumping oxygen out of or into the gap, and the other of the cells serving as an electromotive force cell for generating a voltage according to a difference in oxygen concentration between an oxygen reference chamber and the gap, the apparatus comprising: current or voltage applying means for applying a current or voltage to the electromotive force cell;   V0 voltage detecting means for detecting a voltage V0 across the electrodes at opposite side surfaces of the electromotive force cell;   suspending means for suspending said applying of a current or voltage after the lapse of a predetermined time Ts ranging from 5 to 12 seconds after the heater starts being energized;   V1 voltage detecting means for detecting a voltage V1 across the electrodes at the opposite side surfaces of the electromotive force cell after a lapse of time ranging from 10 ms to 50 ms after said applying of a current or voltage to the electromotive force cell is suspended; and   activity detecting means for detecting a resistance value Rs1 of the electromotive force cell on the basis of said voltage V0 and said voltage V1 and judging that the wide range air-fuel ratio sensor has been activated when said resistance value Rs1 is equal to or smaller than a predetermined value Rss ranging from 1 to 5 kΩ.